Telegraph repeater



Feb. 12, 1935. 1.. A. MORTIMER TELEGRA PH REPEATER Filed Sept. 29, 1933 REPEAT ER A TERMINAL RE PEA TER B SUB 571'4770N C INVENTOR L.A. MOR77MER ATTORNEY Patented Feb. 12, 1935 TELEGRAPH REPEATER Louis A. Mortimer, Hohokus, N. 3., assignor to Bell Telephone Laboratories, Incorporated, New York, N. 32., a corporation of New York Application September 29, 1933, Serial No. 691,482

6 Claims.

This invention relates to two-way telegraph repeaters and more particularly to repeaters of the single line or half duplex repeater type. It is especially advantageous in connection with telegraph systems having large electrostatic capacity and employing machine transmitting and receiving apparatus operating at a high speed, although it is not limited thereto.

In printing telegraph systems, as commonly employed'the signals are transmitted accordance with a five or six unitcode composed of combinations of marking and spacing impulses.

In a single line circuit the speed of transmission of telegraph signals, over lines having considerable electrostatic capacity, is limited because of the time occupied in charging and dis charging the hne. In lines having large capacity, the time required to discharge the line to the potential of the receiving terminal or down to the operating level of the receiving apparatus may extend the previous marking signal over into'the spacing interval, so as to considerably lengthen the marking signals and correspondingly shorten the spacing signals.

' This effect of capacity on telegraph circuits has long been appreciated and it has beenthe practice to ground the line at the transmitting end for a brief interval between signals to permit the line to discharge quickly in the direction of the transmitting end. This principle has been applied to single'lineand half duplex repeaters to provide repeaters for use with single line circuits in which the opposite ends of the outgoing line will be subjected to the same potential at the commencement of a spacing signal, and the line thus be discharged mainly through the transmitting end; The invention is particularly adaptedtothis latter type of repeater.

The use. of telegraph repeaters for single line circuits is becoming more and more extensive, for which reason a simple, practical, high speed repeater will be of importance due to the savings in first cost as well-as in maintenance.

It is an object of the invention to provide an eiiicient, low costrepeater employing one high speed, biased, polarized relay for a given direction of transmission in which the circuit is simplified' so that the relay will have but a single control winding, the biasing of the relay being accomplished by a biasing winding or by other means well known in the art.

Another object of the invention is to provide, in a-single line or half duplex repeater, animproved relay locking arrangement for preventing line or the half duplex type, a-biased polar relay in the single linecircuit, which has a singlewinding serving both as an operating Winding.- and as a locking Winding, and which has a set of repeating contacts. The circuit for the oper-- ating winding, When-marking signals are. being transmitted therethrough, is completedfrom a; source of current to theoutgoing-line through the tongue and marking contact of the opposite line relay, thedistant end of the-line being groundedv or connected to a source of definite potential.

The arrangement is such that, the instant the tongue of the oppositeline relay leaves 'itsmarking. contact in response to a spacing signal, the, circuit including the operating winding of the first relay referred to is completed through a direct current impedance and then directly to the outgoing line. The. resistance-of this circuitefiects an initial reductionin the outgoing line current at the beginning of the. spacingsignaL/ i. e... duringthe travel time of the relay tongue. to its spacing contact to a value sufficienttohold the. first relay locked by its operating winding. during this interval. Upon engagement of the relay tongue with its spacing contact, the locking circuit is completed through the contact directly to ground orto asource of definite. potential;

the spacing contact at the same timeapplies-to theoutgoing line a source of potentialwhichmay beef the same polarity and magnitude as that applied at the opposite end of theline.

Since the opposite ends of the line at thistime are included in a closed circuit, the line discharges rapidly from electrostatic effects and. mainly in the direction of. the transmitting end thereof. The spacing signal, therefore is repeated with substantially full duration and the outgoing line is placed in a discharged condition to respond quickly to'the succeeding marking signal.

In order that the invention may be more fully understood, reference will be had to the accompanying' drawing which is a circuit diagram-0t a single line repeater embodying the invention. The invention as described hereinafter and as illustrated in the drawing is applied to what is usually called a terminal repeater, i. e., a repeater which is used at the terminus of a communication line for repeating the signals between the line and a subscribers line orloop circuit. Thus the terminal repeater B, shown in the drawing, is adapted to receive signals 'from the line east LE, which may be a telephone line equipped with the usual composite sets for simultaneous telephone and telegraph communication over a single line circuit and to repeat the signals into the line west LW, which is a subscribers loop circuit; the repeater B is also adapted to transmit signals from line LW into line LE in the manner of thewell, known single line repeater, that is, the repeater is capable of transmitting in either direction, one at a time.

The line LE shown in the drawing may be a section of a long line circuit with which it is joined by the repeater A, which in this case would be a through repeater; or the line LE may be a local interconnecting line, in' which case the repeater A would be a terminal repeater similar to repeater B for repeating signals directly to or from a distant substation. Ineither case the repeating contacts at repeater A will provide a marking potential opposite that connected to the line LE at the repeater station B. With all the relays of the circuit in marking condition, as shown in the drawing, the marking potential at repeater A is negative and at repeater B positive, as applied to the line LE. When a spacing signal is transmitted by repeater A to the line LE a potential similar to the marking potential at repeater station B is applied thereby producing a no-current condition in the line.

The subscribers loop circuit is closed through the usual printer magnet and transmitting contacts at the. substation C, and the line LW is ordinarily a two-conductor line with a battery supply at the exchange station; in marking position the repeater B applies negative potential to the loop circuit which terminates in a source of positive potential, whereas in spacing condition the repeater B applies positive potential to the line west LW, thus establishing a nocurrent condition in that line.

The marking currents in both lines are ad justed to be about .060 amperes, but it should be understood that other current values may be used and also that it is possible to use other marking and spacing potentials than those specified above without a departure from the spirit of the invention.

The repeater B comprises the line relay WLR for repeating west, the line relay ELR .for repeating east and the break relay EBR associated with relay ELR. These relays are two-winding relays of the polarized type and have armatures which may operate between marking and spacing contacts in, response to received signals. The upper windings are the line windings and thelower windings the biasing windings. The upper windings under the influence of the normal line current tend to operate the relays to their marking contacts and the biasing windings normally tend to operate therelays into spacing positions. The circuit connections are shown in the'drawing in such a manner that by following the electron or negative flow in a given circuit through the relay winding included therein the direction indicates the direction in which the armature will be moved by such a flow; this is indicated in the drawing by arrows marked on the various relay windings, the dotted arrows indicating a special condition.

The repeater station B furthermore comprises a shaping network of any conventional type for preventing the introduction of telegraph thumps into the telephone line LE; it also includes an impedance R for providing a holding circuit for relay WLR during transmission east, which impedance may be any type of direct current impedance, such as a more or less inductive ohmic resistance, permitting a continuous current flow .in the direction of the normal or marking current through the relay, as will be described hereinafter; the repeater also comprises a potentiometer P adapted for the proper supply of biasing and locking currents for relays ELR and EBR under signaling and break conditions, respectively, as willbe described more in detail; the repeater B also includes a two-polarity grounded source of direct current which may be of any convenient type, such as batteries, direct current generators or alternating, current rectiiiers; this current source may be connected through the usual limiting resistances to the various circuits which, however, for the sake of simplicity are not shown in the drawing.

For the description of the operation of this system it will first be assumed that signals are being received from the repeater A over the line LE by the terminal repeater B for retransmission into the line LW and reception and recording at the substation C. Assuming'first that a. marking signal is being received at the repeater B, the negative electron flow for the line E will be as follows From minus potential at repeater A over the line LE into the repeater station B through the shaping network SN, marking contacts of relay ELR, normally short-circuiting the resistance R, and through the line winding of relay WLR to positive potential. This current, as indicated by the arrow, holds the armature of relay WLR in marking position; the lower or biasing winding of relay WLR is permanently connected to receive a negative. current from the minus to the positive potential which, as indicated by the arrow, tends to move the armature into spacing position but which is only about half the strength of the current in the line winding. With the relay WLR. in this condition a negative flow for the line west LW to the substation maybe traced from minus potential over the marking contacts of relay WLR, through the line windings of relay ELR. and EBB, over line LW and through the substation equipment at station C to positive potential. This flow, as indicated by the arrows on the windings, tends to hold the relays ELR and EBR in marking position; a negative flow for the biasing windings of relay ELR and EBR may be traced from minus potential at the marking contact of relay WLR through the lower or biasing windings of relays ELR and EBB in series to a point on the potentiometer P which is of a positive potential with respect to the negative potential, directly ap- When a spacing signal is transmitted from repeater Aby the application ofpositive potentiaito the line LE, the lin'e'cur-rent quickly reduces to zero through the line winding of-r'elay WLR, which then operates to spacing under the influence of the ourrent'in its biasing winding; under this condition positive potential is applied over the marking contacts of break rclay EBR, spacing contacts of relay WLR to the line circuit through the line windings of relays LR and EBB, and the current in this circuit quickly reduces to zero, whereby a spacing signal is received by the substation C; simultaneous with its application to the line circuit over the spacing contact of relay WLR the positive potential is applied to the circuit'through the biasing windings of relays ELR and EBR'to the point of potentiometer P, which in this case is negative with respect to the positive potential at the marking contact of relay EBR; thus, as indicated by the dotted arrows, the biasing current is reversed, the reversal being simultaneously with the decrease of the line current in these relays, thereby insuring that they remain in their marking position during the transmission of a spacing signal through their line windings; and thus a spacing signal will be received by the substation C.

If during the transmission from east to west the substation C sends a break signal by opening the loop circuit for the duration of several impulses, no current can how in the line UN and the line windings of relays ELR and EBB. During a spacing signal coming from the line east LE the relays ELR and EBB will remain in marking position due to the application of positive potential at the spacing contact of relay WLR to their biasing windings. During the reception of a marking signal over line LE the relays ELR and EBR will operate to spacing due to the application of negative potential at the marking contact of relay WLR to their biasing windings. Under this latter condition, negative potential will be applied over the spacing contact of relay ELR to the line LE for the duration of the break signal, which on account of the reversed polarity conditions at the other end of the line LE will constitute a spacing signal at the repeater station A and-any station therebeyond and. will be received as a break signal at those stations. The negative potential at the spacing contact of relay ELR is also applied over the resistance R to the line winding of relay WLR to supply a negative flow in continuation of that caused by the incoming marking signal, the purpose of which is to maintain the relay WLR in marking position preparatory to transmission from west to east upon the cessation of the break signal. The arrangement of resistance R is such that during the travel of the armature of relay ELR from the marking to the spacing contacts the marking current from the line LE will flow with reduced strength over the resistance R through the line winding of relay WLR sumcient, however, to overcome the force of the biasing winding and to hold the relay in marking position until the negative locking potential at the spacing contact of relay ELR is applied to this circuit, thereby preventing the relay WLR. from kicking ofi during the operation of relay ELR.

Now turning to the operation of the system during transmission from west to cast, it will first be assumed that a marking potential is transmitted from the substation C by a complete closureof the loop circuit,in which case a'neg ative flow may be traced from minuspotential at the marking'contact of relay WLR through the line windings of relays ELR and EBB in series over line LW and through the substation equipment to positi-vepotential. At the same time a negative flow may be traced from the marking contact of relay WLR through the biasing windings of relays ELR and EBB in series to the point upon potentiometer P; the strength of the line current being twice that of the biasing current relays ELR and EBR are operated to marking. Under this condition the'line circuit east is closed at the marking contact i of relay ELR and a negative flow may be traced from the marking contact at repeater A over the line LE, marking contact of relay ELRand through the line Winding of relay WLR to positive potential, which places this relay in marking position.

When a spacing signal is transmitted from the substation C by the opening of its transmitting contacts, the line current in line LW reduces to zero, thereby permitting the biasing windings of relays ELR and EBR to operate the armatures into spacing position; in this case the resistance R functions, as already described, to maintain a-reduced line current from'the line LE through the line winding of relay WLR during the travel of the armature of relay ELR, surficient to securely hold the armature of relay WLR against its marking contact until negative potential is applied over the spacing contacts of relay ELR to lock relay WLR in kick-oiT of the relay WLR and mutilation of the signals received from the substation are prevented. Relay EBB, When operated to spacing, applies negative potentialover its-spacing c0ntacts tothe spacing contacts of relay" WLR."

Thus a spacing signal will be line LW to the'line LE. 7

If new a break signal arrive from repeater A by the prolonged application to line LE of a positive potential atthat station, and'while a spacing signal is being transmitted from west to east, a normal line current will flow from negative potential at the spacing contact of relay ELR over the line to positive potential at repeater A. When during the break signal from line LE a marking potentialis transmitted by substation C, causing relays ELR and 'EBR to operate to marking the armature of relay ELR, as it leaves its spacing contact, will remove negative potential from the line circuit and from the line winding of relay WLR, so that the biasing current will operate relay WLR to spacing; when the armature of relay EBR reaches the marking contact positive potential is applied to the spacing contact of relay WLR. with the result that a spacing signal will be transmitted to the substation C for the duration of the break signal, and that relays ELR and EBR will remain locked in marking position due to the negative flow from the relatively negative point on potentiometer P, the biasing windings in series of relays EBR and ELR, over the spacing contacts of relay WLR and marking contacts of relay EBR to positive potential.

This locking circuit being underthe control of only relay WLR no signals can pass from west to east.

It will be seen that only a single two-winding relay is required for all the functions of retransmitting ordinary as well as break signals incoming over a line section into another line section and that by the provision of an impedance repeated from the its marking position; thus 5 bridging the marking contacts of the line relay relay may be prevented from kicking off during transmission in the opposite direction of ordinary as well as break signals. Thus, even though these principles have been shown applied to a terminal repeater station, it is evident that these general arrangements are equally applicable to repeaters of other types; these features, therefore, may also be incorporated in the repeater station A, shown schematically in the drawing, for the proper cooperation with the terminal repeater B.

In order that the appended claims may be readily applied to the embodiments of the invention shown, the line LE may be considered the incoming line, relay ELR. being the transmitting relay and relay WLR the receiving relay for this line. It is to be understood, however, that the repeater, as claimed, may provide for transmission of signals in either direction.

What is claimed is: I

1. In a signaling system, a west repeating polar relay having biasing means and a single control winding, an east repeating polar relay having repeating contacts, a direct current impedance separate from the windings of said relays and connected in series with said control winding to reduce the current therein to a holding value during repeating of a spacing signal by said east relay, said repeating contacts being connected to directly bridge said resistance to increase the current in said control Winding during repeating of a marking signal by said east relay.

2.111 a signaling system, a west repeating relay having a continuously energized biasing winding and a single control winding in the east line, a resistance in the east line circuit, an east repeating relay having repeating contacts in a path connected directly in shunt to said resistance for increasing the current in said control winding from holding value to marking value when closed for repeating a marking signal. v

3. In a signaling system, incoming relay means for repeating signals from an incoming line to an outgoing line, outgoing relay means for repeating in the opposite direction, said incoming relay means having biasing means and a single control circuit including a source of potential different from'that of the incoming said marking contacts and a source of holding potential connected in circuit with said control winding when said transmitting relay is out'of its marking position. 1

5. A repeater having an incoming line relay and an outgoing line relay, the incoming line relay repeating to an outgoing line and the outgoing line relay repeating to anincoming line, a single, control winding for said incoming line relay, a resistance, circuit means for said control winding normally completed through the marking contacts of the outgoing line relay to the incoming line, said circuit being completed during the transmission of spacing signals into said incoming line through thesaid resistance and the spacing contacts of said outgoing line relay independently of the incoming line,-and said circuit being completed during the time the marking contacts of the outgoing line relay are open directly through said resistance to said incoming line.

6. A telegraph repeater having an incoming line relay and an outgoing line relay, a direct current impedance, a, single control winding for said incoming line relay, the circuit for said control winding, being completed directly through the incoming line when marking signals are being transmitted by said outgoing line relay, and said circuit being completed through said impedance when the marking contacts of said outgoing line relay are open, and means for connecting the end of said incoming line at the repeater to a source of potential of the same polarity and magnitude as the distant end of the line, when the outgoing line relay closes its spacing contacts.

LOUIS A. MORTIMER. 

